Sildenafil is a selective inhibitor of cyclic guanosine monophosphate (cGMP)-specific phosphodiesterase type 5 (PDE5). PDE5 is the predominant isozyme that metabolizes cGMP formed in the corpus cavernosum. Sildenafil is thought to enhance the effect of nitric oxide due to its inhibitory effect in the corpus cavernosum. The enhanced effect of nitric oxide therefore increases the cavernosal blood flow in the penis and lungs.
Sildenafil citrate is commercially available as a film coated tablet (Viagra®, available from Pfizer Inc.) for the treatment of erectile dysfunction. However, the reported bioavailability of this formulation is only 40%.
Sildenafil citrate is also commercially available in formulations for the treatment of pulmonary arterial hypertension. One such formulation is a film coated tablet (Revatio®, available from Pfizer Inc.).
“Sublingual” means “under the tongue” and refers to administration of a substance via the mouth in such a way that the substance is rapidly absorbed via the blood vessels under the tongue. A sublingual formulation is desirable because it bypasses hepatic first pass metabolic processes which provide better bioavailability, rapid onset of action, and higher patient compliance. Dysphagia (difficulty in swallowing) is common among in all ages of people and more common in geriatric patients. In terms of permeability, the sublingual area of oral cavity is more permeable than buccal area. Sublingual drug administration is applied in field of cardiovascular drugs, analgesics, steroids, enzymes and barbiturates.
U.S. Pat. No. 6,548,490 is directed to methods for treating erectile dysfunction including sublingually administering a composition that can include sildenafil. This method requires that the composition be in the form of a tablet, cream, ointment or paste. U.S. Pat. No. 8,133,903 discloses a method that includes administering up to 1.5 mg/kg/day of a PDE5 inhibitor, such as sildenafil, for not less than 45 days. This patent, however, also fails to disclose a fast acting oral spray formulation.
US Patent Application Publication No. 20130059854 discloses a method for mitigating erectile dysfunction by administering a composition orally that can include sildenafil. This formulation requires the use of sucrose fatty acid esters. U.S. Pat. No. 7,758,886 is directed to an aerosol composition including a poorly water-soluble active agent, such as sildenafil. This patent teaches that tyloxapol, polysorbates, vitamin E TPGS, or macrogol-hydroxystearates, and a phospholipid component, are required for administration. U.S. Pat. No. 6,585,958 discloses an aerosol formulation that may contain sildenafil. This formulation, however, requires a pressure-liquefied propellant mixture that includes dinitrogen monoxide and other components. In addition, US Patent Application Publication No. 20130143894 discloses a sildenafil oral spray formulation wherein the pH is from about 1.5 to less than 3.0. This application, however, teaches the use of a polar solvent such as propylene glycol and ethyl alcohol.
While there are various sildenafil formulations currently available, there is still a need in the art for a quick-onset sublingual spray formulation containing sildenafil.